Community antenna television (“CATV”) networks have been used for more then four decades to deliver television programming to a large number of subscribers. Increasingly, CATV networks are used by providers to provide data services to subscribers. For example, cable modems used in a broadband cable modem termination system (“CMTS”) compete with digital subscriber lines (“DSL”) and DSL modems used therein, which are typically implemented and supported by telephone companies. DSL service is typically provided over the same wires as a residence's telephone service.
In the cable distribution context, a CMTS typically transmits downstream data to a broadband device, typically a cable modem (“CM”). The data sent to a CM can include packets containing voice call information, internet data, or video content, for examples. In the scenario where a program (audio or video) is transmitted downstream from the CMTS to a CM, multiple content streams may be served by multiple downstream channels within a media access control (“MAC”) domains. Different MAC domains may be located at the same service provider head end, or may be geographically spread amount multiple head end locations.
When a user is receiving a program (audio or video) and wishes to change to a different program, the user typically causes a set top box, or such similar subscriber device, to request a different content stream that corresponds to the new program the subscriber wishes to receive. The subscriber device typically uses IP multicast signaling protocols, such as IGMP or MLD, to request the content stream. The subscriber device only has knowledge of the content stream identifier, typically an IP multicast address (ASM/SSM), and is not provided details of whether the content stream is currently being forwarded by the CMTS or on what downstream channel, within the set of downstream channels the CMTS controls within the DOCSIS MAC domain, it may currently be available on. The CMTS receives the IGMP/MLD request. The CMTS controls the content streams that are delivered to subscriber devices and downstream channels that are used for delivery. If a content stream is not presently available from the CMTS, the CMTS requests the content stream. The CMTS decides what downstream channel to deliver the content on based on available bandwidth or some other form of policy settings configured on the CMTS. In addition, the requested content stream may already exist on one of the downstream channels. In either case, once the downstream channel is identified by the CMTS, and the subscriber device is identified as being on a different downstream channel, the CMTS invokes the DCC procedure to move the subscriber device to the correct downstream channel. This results in the subscriber device performing a CMTS-driven re-tune of its downstream channel in order to receive the requested content stream. The DCC procedure uses a somewhat complicated and involved process for signaling intention of channel change, waiting for the channel change to occur, followed by acknowledgement of the channel change. A number of re-initialization techniques are available to DCC to ensure that the subscriber device can be successfully readmitted to the DOCSIS MAC domain, without causing interruption to the subscriber device or other subscriber devices in the network. The selection of some of these techniques can induce a time delay that impact the subscriber device to quickly access the content stream that was requested in the first place. The DCC procedure, due to its complexity, ties up resources on the CMTS and may be limited, depending on the CMTS architecture, to a possibly low number of concurrent transactions per second.
The DCC process can take a long time relative to the amount of time a user may be used to in changing television stations between two analog-delivered channels. This time delay can be annoying and tarnish a viewers experience in using his or her television, or other similar video monitor device. The DCC process can also increase the amount of interactivity between subscriber devices and the CMTS, leading to an increase in upstream bandwidth usage as well as increasing the processing demands of the CMTS.
Thus, there is a need in the art for method for facilitating the changing of channels delivering different video content that reduces the amount of time between channel changes when the different program channels are served by different downstream channels within DOCSIS MAC domains.
Information regarding multiple content streams delivered from a given MAC domain is typically not provided to a CM. Delay exists when accessing content from different downstream channels from the same MAC domain. The delay occurs when the CM requests a content stream and waits for the CMTS to either deliver the new content stream on the currently tuned downstream channel, or, by using DCC, change to the downstream channel the content stream already exists on before a user can access the required program stream. Thus, there is a need in the art for reducing the time between accessing programs streams that are delivered within the same MAC domain but on different downstream channels.